Electrically reconfigurable optic devices direct optical signals along selected fibers, or control optical signal intensity within a fiber link, or select wavelength band of an optic network in which light signals are transmitted along optical fibers to transfer information from one location to another. Optical devices of this type should have the following performance characteristics: high speed operation, low optical insertion loss, high reliability, low power consumption, easy to drive, and low cost to produce. Although reconfigurable optical devices become increasingly important in today's optical networks, they have not been widely adopted because of their poor optical performance and complex control requirements.
Reconfigurable optical devices are dominated by those with mechanical switching mechanisms, due to their low cost and good optical performance of low loss and little signal distortion. Unfortunately, these switches are slow and not sufficiently reliable.
Non-mechanical, solid-state optical, switches are more desirable due to their intrinsic high speed operation and excellent reliability as well as low power consumption. Many non-mechanical configurations have been reported based on mechanisms such as liquid crystal polarization rotation, thermal heating induced optical birefringence change, magneto-optic polarization rotation, and electro-optic retardation that changes either optical phase or polarization. For additional background on such switches that use organic liquid crystals the reader is referred to U.S. Pat. No. 4,917,452. Further information on the use of ceramic materials in such switches is taught in U.S. Pat. Nos. 6,330,097; 6,757,101.
Among these methods, devices based on inorganic electro-optic crystals are most desirable, since this class of materials has the highest operation speed know to date. One example is LiNbO3 that has a high Curie temperature near 2000° C., making it a highly stable electro-optic material of choice for practical applications. However, a straightforward application of electro-optic crystals in conventional device configurations lead to the requirement of excessively high driving voltages well over several thousand volts, rendering it impractical. Diffusion based LiNbO3 waveguide technologies have been developed that reduce the driving voltage significantly. Also, the use of selective domain poled electro-optic materials, such as LiNbO3 wafer to reduce drive voltage to about 700 V is found in U.S. Published Application 2002/0136482. However, the planar waveguide platform inherently has high polarization sensitivity and operation bias drift. Both of these issues have to be dealt with using difficult schemes, and the fundamental mode miss-match with the fiber generates unacceptable large insertion loss.
U.S. Pat. Nos. 6,137,619 and 6,404,538 both to Chen et al. teach a high-speed electro-optic modulator that uses a ceramic material that exhibits a large electro-optic effect and is coupled with conventional fiber collimators. Due to its low Curie temperature, the electro-optic ceramic material exhibits instabilities such as large temperature dependence and large hysteresis, consequently requiring complex compensation or feedback control. Moreover, the switching times of devices using such material are often limited to several microseconds due to polycrystalline material structure, thus limiting the applications of such devices.
Further prior art teachings concentrate on other aspects of the optics in electro-optic devices to improve their performance. For example, U.S. Pat. Nos. 6,542,665 and 6,839,483 both to Reed et al. teaches the uses of GRIN lenses for collimating down to a beam diameter D on the order of fiber diameter 125 μm over a longer Raleigh range. U.S. Pat. No. 6,873,768 to Duelli et al. teaches fiber terminations to form a microlenses and achieve good collimation and/or focusing to thus extend the working distance with the minimum spot size (or beam diameter D) for free space interconnects and other devices. Still other teachings regarding working distances and optics can be found in U.S. Pat. Nos. 6,890,874; 6,839,485 and U.S. Published Applications 2002/0094162 and 2003/0021531.
Unfortunately, none of the prior art teaches or points the way to an apparatus that can use electro-optic materials to operate on beams efficiently and with low loss. Therefore, a micro-optic platform that overcomes these deficiencies and the deficiencies associated with waveguides, as discussed above, would be of significant commercial value and represent an advance in the art for electrically controllable fiberoptic devices.